This invention relates generally to temperature sensing and more particularly to temperature sensing of hydraulic fluid used in vehicular transmission systems.
In recent years, it has become conventional in the motor vehicle art to control various functions by means of microprocessor based controls to obtain performance improvements. For example, in automatic transmissions solenoid valves are used to effect gear shifting and valve actuation is sensed by placing pressure switches in communication with hydraulic lines so that a change in pressure in such lines which occurs upon valve actuation and de-actuation can be sensed with a suitable electrical signal provided to the microprocessor as a result of the switching. Switch assemblies of this type are shown for example in U.S. Pat. Nos. 4,861,953; 4,853,503; 5,004,876; 5,101,549 and 5,015,808.
Another relevant control input to the microprocessor is the temperature of the hydraulic fluid since the viscosity of the fluid varies with temperature. It is known to drill and tap a bore in the transmission housing in communication with a hydraulic line and to insert a temperature probe mounted on a threaded base into the bore and to connect a suitable electrical lead to the microprocessor. Although this provides the required data in a satisfactory manner it requires separate operational steps to set-up the transmission housing in a drill press, drill and tap the bore as well as handling the separate electrical lead and therefore involves an undesirable cost.
It is an object of the present invention to provide temperature sensing apparatus for use with vehicular transmission systems, particularly with automatic transmission systems, which is less expensive to install than prior art sensors and yet which are reliable and durable.
Other objects, features and advantages of the invention will be apparent from the following detailed disclosure taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts.